1. Field of the Invention
The present invention relates to a zoom lens and an image pickup apparatus. In particular, the present invention relates to a technical field of a zoom lens suitable for an imaging optical system in a digital input/output apparatus and of an image pickup apparatus including the zoom lens.
2. Description of the Related Art
In recent years, a compact image pickup apparatus, such as a digital video camera or a digital still camera, has become popular. In such an image pickup apparatus, it is demanded to increase a lens performance of a zoom lens to meet increase in the number of pixels of an image pickup device. Also, the image pickup apparatus is desired to be reduced in size. Owing to this, it is demanded to reduce an overall length of the zoom lens. Further, manufacturing of the image pickup apparatus is desired to be facilitated to increase productivity by decreasing a sensitivity of decentration.
Zoom lenses mounted on image pickup apparatuses, for example, digital still cameras, involve various types of zoom lenses. One of such zoom lenses mounted on the image pickup apparatuses and reduced in size is a zoom lens including three lens groups including a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power arranged in that order from an object side to an image side (for example, see Japanese Unexamined Patent Application Publication Nos. 2002-244043, 2004-191599, and 2007-212777).
A zoom lens disclosed in Japanese Unexamined Patent Application Publication No. 2002-244043 includes a second lens group including two cemented lenses having positive refractive powers.
A zoom lens disclosed in Japanese Unexamined Patent Application Publication No. 2004-191599 includes a second lens group including two cemented lenses. The second lens group includes five lenses in total, i.e., three positive lenses and two negative lenses.
A zoom lens disclosed in Japanese Unexamined Patent Application Publication No. 2007-212777 includes a second lens group including a single lens having a positive refractive power and a cemented lens having a negative refractive power and including two lenses.